Birnesite specimen

I would like to purchase this from a friend but do not know what to offer him?
I have few other specimens put a side and may want to make an offer for all of this as a lot.
Any ideas?

How large is this specimen?

Rock Currier
Crystals not pistols.

It is about 3 3/4" long and about 1" wide and very sharp.

I assume it is a pseudomorph after serandite? Its a nice specimen. Perhaps $200. Those who dig St.Hilaire specimens really like them. Perhaps even a bit more. It will appeal to pseudomorph collectors as well. I have seen substantially larger specimens of this type.

Rock Currier
Crystals not pistols.

Thanks again
"I have seen substantially larger specimens of this type."
this helps me in making my decision, my friend asked for $500 and after your info I will offer him $300. I may go for another hundred more But will think about it. All this dealing puts me a little in a conflict of interest since he is asking me to sell this stuff for him and now I want it myself. Should I feel uncomfortable about this?

$500 seems emminently reasonable for such a sharp and large example of a unique pseudomorph, especially considering how long ago they came out, and the fact that MSH is basically kaput as a source of minerals...